The present invention relates to a device and method for heating a positive crankcase ventilation system so that, in particular, icing of the crankcase ventilation system will be prevented.
Vehicles with so-called hybrid drives have existed for some years as energy saving and environmental friendly alternatives to conventional internal combustion engines. A hybrid drive is usually defined as the combination of a variety of drive principles or the combination of a variety of energy sources for the respective type of drive. Therefore, a hybrid drive generally exhibits two different energy converters and two different energy accumulators. Except for a very few exceptions, in the practical implementation the energy converter involves an internal combustion engine and an electric motor, and the energy accumulator involves a combustible fuel and a battery.
In a vehicle with a hybrid drive both the internal combustion engine and the electric motor can be operated in a respectively optimal efficiency range. Excess energy, for example when braking or during passive coasting, is used via a generator for charging the battery.
When accelerating, the internal combustion engine and the electric motor usually work together, so that, in comparison to a typical internal combustion engine, a smaller engine can be used. Since an internal combustion engine can deliver a very high torque—especially in a higher speed range—the reserved electric motor is more suitable, in particular at start-up, because it can provide a maximum torque even at low speeds. Therefore, in the case of certain driving dynamics both the internal combustion engine and the electric motor can be activated and deactivated, in order to achieve a driving performance that exhibits optimal energy consumption with high efficiency.
Therefore, when hybrid vehicles are in operation, there is frequently the situation that the internal combustion engine is deactivated during the trip. Therefore, in the past, the positive crankcase ventilation system has been known to ice up in conventional vehicles. Positive crankcase ventilation is necessary because gases and unburned fuel can flow on a regular basis from the combustion chambers of the internal combustion engine into the oil circuit. If it is not possible to ventilate, for example, by way of a valve in the crankcase, a dangerous pressure can build up inside the housing and cause damage to the engine.
Especially at low temperatures, for example below 5° C., the air flow conditions produced while driving and the evaporation coldness may cause parts of the crankcase to ice up. Protruding parts, like the ventilation valves or the hoses, which are supposed to remove gases from the interior of the crankcase, are exposed to an especially high risk. Hybrid vehicles, in particular, are exposed to this risk because their analogous parts may cool down faster in a hybrid driving mode when the internal combustion engine is deactivated. In addition, the risk of icing in hybrid vehicles is higher, because the internal combustion engine is often switched off. Moreover, in the event that the internal combustion engine is running, it is running under a high load and, thus, at especially large throttle flap angles. Therefore, an especially strong cold air flow can cause the ventilation system to cool down.
In the past it has been proposed, for example, in the case of conventional motor vehicles, which exhibit only an internal combustion engine, to heat the respective ventilation valves with an electrical heating system in order to prevent the valves from icing. This heating system requires an additional current supply and wiring between the parts to be heated.
The present invention provides an improved device for avoiding icing of the crankcase of an internal combustion engine in a hybrid vehicle.
The inventive device for heating a positive crankcase ventilation system, in particular for that of a hybrid vehicle, has the advantage that, independently of a closed circuit cooling system for the internal combustion engine, which may cool down especially when only the electric motor is running in the hybrid mode, the ventilation system is heated and cannot ice up.
Almost all hybrid vehicles must provide a low temperature or supercooling cycle, which cools the components of the power electronics for the control of the electric motor. Therefore, the invention does not require any additional, for example, an electric, heating system, which entails a higher energy consumption of the entire vehicle.
According to one embodiment of the invention, the supercooling cycle exhibits a first cycle for cooling the power electronics and a cooling subcycle for heating the ventilation system. In this case, the coolant flow rate through the cooling subcycle is configured so as to be controllable. Suitable ventilation devices include, for example, a ventilation valve, a port in the housing, and/or a ventilation hose. At least one follow-up pump is advantageously provided in the supercooling cycle. In order to adjust the coolant temperature in the supercooling cycle (or also the subcycle) to approximately 70° C., a temperature control unit may be provided. For example, a coolant flow rate control unit and a heat exchanger are contemplated, so that when the coolant passes through the subcycle or supercooling cycle, it dissipates thermal energy to the environment.
The invention also provides for applying the device for heating a positive crankcase ventilation system in a hybrid vehicle. In this case, the crankcase is assigned to the internal combustion engine. Therefore, according to the invention, a pre-existing cooling cycle, which usually operates at high coolant temperatures of approximately 100° C., is not used for heating the crankshaft ventilation, but rather portions or a branch of the supercooling cycle are preferably used.
The power electronics exhibits, for example, semiconductor transistors, voltage converters, and/or switching devices having a predefined temperature stability. In one embodiment, the ventilation devices can be heated exclusively by use of the supercooling cycle. However, another embodiment also provides a cooling subcycle for heating the ventilation devices. This cooling subcycle can be supplied with coolant from the closed circuit cooling cycle of the internal combustion engine and/or from the supercooling cycle by way of a controlled valve unit. Thus, it is possible to mix in a controlled manner the coolant, which is identical in design, in order to adjust the temperature of the ventilation devices at the positive crankcase ventilation, for example, as a function of the outside temperature.
The temperature is controlled, preferably, in such a manner that heating the ventilation devices prevents said ventilation devices from icing.
In a preferred embodiment, a heating control unit (or rather a temperature control unit) controls the controllable valve unit in such a manner that in one operating state of the hybrid vehicle, in which the internal combustion engine is deactivated, the coolant is conveyed in essence from the supercooling cycle into the cooling subcycle, whereas in another operating state of the hybrid vehicle, in which the internal combustion engine is activated, the coolant is conveyed in essence from the closed circuit cooling system of the internal combustion engine into the cooling subcycle. In this way, when the internal combustion engine is running, its closed circuit cooling system can be additionally cooled, for example, by heating the ventilation devices, because heat from the respective coolant is transferred to the ventilation devices.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.